Iron is one of the elements undoubtedly known to the ancient world. Using of Iron is increasing every day and it is important to find new sources.
Economical extraction needs high grade source of iron and it is essential to convert low grade iron ore to high grade one.
low grade hematite are abundant and by conversion hematite to magnetite it is possible to get high grade iron ore.
There are some methods to convert hematite to magnetite but there is this question it is conceptually right to convert hematite to magnetite and magnetically separate them to get high grade iron ore? Are hematite to Magnetite Conversion economical with CO and C?
I heard there are some companies in China but i could not find any information of them in English search.
The formation of magnetite at low temperature was thermodynamically more favorable in CO compared to the H2 atmosphere. The thermodynamic calculation revealed that CO acts as a better reducer than H2 as the enthalpy change of a reaction is more exothermic than H2 and the change in Gibbs free energy (DG) at about 500 C is directed to more spontaneous reaction in converting Fe2O3 to Fe3O4.
I would not think it is worthwhile to convert Haematite to Magnetite. Magnetite is mined in many places around the world. It is also a by-product of heavy metal beach sand mining (ie Rutile-zircon mining). It is recovered and concentrated with magnetic separators. Tens of years ago I visited the Savage River magnetite mine in Tasmania Australia. The ore was milled and concentrated at the mine then piped 85km as a slurry to Port Latta (near Burnie) recovered by magnetic separators pelletised and reduced with anthracite coal to pellets of 95% Fe which then could be made into steel in electric furnaces.
There are two common conversion processes involving Fe2O3 and Fe3O4.
(1)Fe3O4+ 4 CO→3 Fe + 4 CO2
Fe2O3+ 3 C→2 Fe + 3 CO
The process most frequently cited when it comes to a conversion of Fe oxides is the smelting of Fe oxides and their conversion into native / metallic iron as it is done in blast furnaces. These equilibrium reactions are a function of the temperature. At T > 800°C the reaction is shifted to the right-hand side. During the so-called Boudouard equilibrium reaction the resulting carbon dioxide reacts with coke to form carbon monoxide.
(2) A different process is the production of Fe magnetic pigments. This conversion, however, is very delicate as to the preservation of the grain morphology and coercive field strength and does not involve C and CO. The needle-shaped magnetic pigments have acicular alpha-FeOOH and gamma-FeOOH as starter which are produced artificially from Fe(II) solutions. The second part of the process runs from the Fe oxide-hydrate through gamma Fe2O3 to Fe3O4 and Fe at T < 500°C by means of dehydration and reduction.
From the economic point of view only the second process makes sense. The smelting process is the common way of creating metallic iron.
Maybe there are special processes to obtain magnetic material according to the second processes (?). This is, however, out of my field of experience.
H.G.D.
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